JKS - The Mini with Audirvana will be better than most reclockers added to the Sonos, provided you play .wav files and not FLAC, AIFF or ALAC on the Mini and have an external linear DC power supply for the Mini, however, the Synchro-Mesh reclocker will beat this as well as most USB interfaces, except for the Off-Ramp 5. The Synchro-Mesh reclocker is not cheap ($599), but it delivers world-class sound from a Sonos or any other digital source.
http://www.empiricalaudio.com/products/synchro-mesh
It can be further improved by upgrading the power supply to a Dynamo ($749) and adding a world-class BNC-BNC coax cable with RCA adapters ($250). Putting more money into your source is never a bad idea. If you have a poor source, there is little that can be done downstream to fix this.
See reviews on the Synchro-Mesh. It delivers the best sound of any reclocker on the market:
http://www.empiricalaudio.com/news-and-reviews/synchro-mesh
30-day unconditional money-back guarantee, less shipping.
Steve N.
Empirical Audio
Est. 1996